A 55-year-old female patient presented with an asymptomatic, hyperpigmented, rough plaque over her right cheek of 2 months duration. She had no other complaints. She had undergone surgery for carcinoma of the lip 2 months back followed by flap transfer. She developed this lesion insidiously a few weeks after surgery. On examination, the patient had a single, hyperpigmented, well-defined verrucous plaque having a "stuck-on" appearance, of size 5 cm × 6 cm on the right cheek over a small surgical scar measuring 4 cm [Figure 1]. We considered differential diagnoses of seborrheic keratoses, cutaneous metastases, terra firma forme dermatoses (TFFD) and dermatitis neglecta (DN). On wiping the lesion with swab soaked in ethanol, the lesion was completely removed and underlying normal skin was revealed [Figure 2].

The term "DN" was first coined by Poskitt et al. in 1995. [1] It is characterized by hyperpigmented, waxy, verrucous plaques secondary to poor skin hygiene, which may be due to psychiatric illness, neurological deficit, surgical scar, hyperesthesia, periorbital eczema or even a benign nevus. [2] It is said to occur due to incomplete exfoliation and consequent accumulation of sebum, sweat, corneocytes and keratin material. TFFD or "Duncan's dirty dermatoses" is another similar condition; however certain differences have been noted in literature [Table 1]. [3],[4],[5] Other differentials include some "dirt-like" lesions such as atopic "dirty neck," acanthosis nigricans, confluent and reticulate papillomatosis and hyperkeratotic head and neck malassezia dermatosis. [3],[5],[6] It can mimic certain conditions like psoriasis. [7] Dermatitis artefacta is another differential diagnosis to be considered. It is usually seen in people with underlying personality disorder and is an act of commission; in contrast, DN is an act of omission. [1],[3]

Our patient had a pigmented plaque on her face closely resembling seborrheic keratosis. The short duration and history of surgery made us suspect DN, causing immediate relief and surprise in the patient and her oncologist. Both DN and TFFD, if correctly diagnosed, are highly gratifying to the treating physician as they are instantly removable and cured. Early and correct diagnosis can prevent unnecessary and expensive investigations.